PHOTOELECTRIC CHARGING of DUST GRAINS in PROTOSTELLAR DISKS Prof. Ana I. Gómez de Castro Universidad Complutense de Madrid and Dr. Andreas Pedersen Helsinky University

MENU Motivation – Protostellar disks: –mass transfer –disk-star interaction Photoelectric charging Disk atmospheres Summary

PROTOSTELLAR DISKs Dusty disks are observed around protostars with masses < 10 Mo HH 30 Jet engine (mas-μas scales)

Protostellar disks are formed in the gravitational collapse provided angular momentum is transported Mass infall from a rotating core produces a flattened structure

DISK INSTABILITIES No hydrodynamical instabilities – Disks are stable against Rayleigh- Taylor Instabilities Gravitational instabilities Magnetorotational instability

Gravitational EnginesProf. Ana I Gómez de Castro – Univ. Complutense Transport can also be allowed by wind ejection that shields the disk The properties/efficiency of the disk wind is defined by three basic parameters:

DISK IONIZATION is fundamental for transport to work

PROTOSTELLAR DISKS IONIZATION Stellar UV photoionizing photons penetration Chemical abundances in the disk

Xrays and relativistis particles ionize the interior of the disk The electrons will be absorbed by the dense environment producing X-ray radiation UV radiation photoionizes the disk atmosphere (MgII) UV radiation photodissotiates H2 and produces a faint wind Transmitted X-ray

THE DUSTY ATMOSPHERES OF DISKS ---- why?? THE PROPERTIES OF THE DUSTY ATMOSPHERE CONTROL: WIND EJECTION DISK PROTECTION AGAINST STELLAR IONIZATION AND MAY INFLUENCE THE DISK-STAR BOUNDARY LAYER

Gravitational EnginesProf. Ana I Gómez de Castro – Univ. Complutense The current paradigma ISO & Ground-Based IR Interferometers XMM-Newton Chandra Hubble Space Telescope WSO-UV

OBJECTIVES TO EVALUATE THE IMPACT OF THE STELLAR FIELD IN DUST IONIZATION PHOTOELECTRIC DISK CHARGING PROFILE CHARACTERISTICS OF PHOTOELECTRONS RELEVANCE OF PHOTOELECTRIC CHARGING IN DUST GRAINS CHARGING IN PRE-MAIN SEQUENCE SOLAR SYSTEM ANALOGUES

UV Radiation from protostars

The photoelectric dust charging profile depends on the UV field

Two populations of photoelectrons Low energy population E=2.5 eV --- dispersion 1.2eV High energy population E=5.8eV– dispersion 1.4 eV above the photodissotiation threshold of H2 (4.52eV) contributes to the ionization of Mg (7.64eV)

DUST CHARGING EQUILIBRIUM CONDITION: Collisional loses by electron impact = Photoelectric charging

DUST CHARGING Photoelectric Charging

Gravitational EnginesProf. Ana I Gómez de Castro – Univ. Complutense CONCLUSIONS DUST CHARGING BY PHOTOELECTRIC EFFECT IS DOMINANT IN THE INNER BORDER OF THE DISK TO Q  e- SECONDARY ELECTRONS HAVE ENERGIES HIGH ENOUGH TO PHOTODISSOTIATE H2 THE ATMOSPHERE OF PROTOSTELLAR DISKS CAN BE CONSIDERED AS METHAL-LIKE

Gravitational EnginesProf. Ana I Gómez de Castro – Univ. Complutense Disk-star interface Lovelace et al Field lines are twisted by the differential rotation 2.Toroidal magnetic flux is generated out of the poloidal flux 3.The toroidal field builds up and the associated field pressure tends to push the field lines outward 4.The magnetic link between the star and the disk is eventually broken.

Gravitational EnginesProf. Ana I Gómez de Castro – Univ. Complutense Engine at work

Gravitational EnginesProf. Ana I Gómez de Castro – Univ. Complutense Engine at work… With disk dynamoWithout disk dynamo

Gravitational EnginesProf. Ana I Gómez de Castro – Univ. Complutense UNKNOWNS Current layer & reconnection Inner-disk boundary in black-holes Blandford-Znayek effect Disk ionization degree Mass feeding the disk Inner disk boundary Vertical structure & instabilities OUTFLOWS DISKS